Remove -Q option on flycheck-emacs-command. 

Removes -Q option on flycheck-emacs-command. It is replaced wih -q and add optional --no-site-file --no-site-lisp
Currently -Q disables site-file and removes site-lisp directories from load-path.

With -Q option there is no way to add system-wide packages installed with apt-get on Debian systems to load-path.

This modification allows to enable or disable site-lisp on demand.

By default site-lisp is enabled. So, Debian/Ubuntu users will have Emacs packages installed via apt on their load-path.
Setting this option to non-nil is equivalent of -Q.